**FILE** Dr. Robert Stern, right, and Chris Nowinski, left, confer before answering a reporter's question at the Boston University Center for the Study of Traumatic Encephalopathy news conference about the finding of Chronic Traumatic Encephalopathy in the brain of former NFL player Dave Duerson in Boston, Monday morning, May 2, 2011. Duerson committed suicide in February. Dr. Robert Cantu, MD, is at center. (AP Photo/Stephan Savoia)

FILE - In this Aug. 14, 1989, file photo, Chicago Bears safety Dave Duerson (22) scrambles for running room after intercepting a pass as Miami Dolphins Jeff Uhlenhake (63) grabs hold during an NFL football game in Miami. Duerson, a four-time Pro Bowl safety who played on Super Bowl winners with the Chicago Bears and New York Giants, has died. He was 50. Miami-Dade Police Detective Robert Williams says Duerson's body was found Thursday in Sunny Isles Beach, Fla. Investigators have not determined the cause of death. (AP Photo/File)